(19)
(11) EP 1 219 379 A3

(12) EUROPEAN PATENT APPLICATION

(88) Date of publication A3:
17.07.2002 Bulletin 2002/29

(43) Date of publication A2:
03.07.2002 Bulletin 2002/27

(21) Application number: 02003384.1

(22) Date of filing: 10.09.1997
(51) International Patent Classification (IPC)7: B23K 11/24, B23K 11/25
(84) Designated Contracting States:
DE FR GB IT NL

(30) Priority: 11.09.1996 JP 26243896
24.10.1996 JP 29927196
24.10.1996 JP 29927296

(62) Application number of the earlier application in accordance with Art. 76 EPC:
97307014.7 / 0835713

(71) Applicant: MIYACHI TECHNOS CORPORATION
Noda-shi, Chiba-ken (JP)

(72) Inventors:
  • Mukai, Ren, c/o Miyachi Technos Corporation
    Noda-shi, Chiba-ken (JP)
  • Fujisawa, Masaaki, c/o Miyachi Technos Corporation
    Noda-shi, Chiba-ken (JP)

(74) Representative: Makovski, Priscilla Mary 
BARKER BRETTELL 138 Hagley Road
Edgbaston Birmingham B16 9PW
Edgbaston Birmingham B16 9PW (GB)

   


(54) Method and apparatus for controlling resistance welding


(57) An apparatus for controlling resistance welding defines a weld time for series welding as a plurality of (e.g., two) weld periods. In one embodiment, a control (56) successively switches a bidirectional switch (30) in a first polarity during the first weld period so that welding current flows through workpieces of different metals in one direction by passing through a series of welding points of the workpieces. In the second weld period, the control (56) successively switches the bidirectional switch (30) in the reversed polarity so that welding current flows through the workpieces in the other direction so as to compensate for Peltier effect on the welding points. A polarity changing technique is used to minimize welding energy loss in shifting weld periods for better weld quality. In another embodiment, thyristors (66,68) are controlled such that they are fired in the second half cycle of the supply voltage (E) at an angle smaller than the firing angle in the first half cycle.






Search report